The dishwasher sprays detergent and washing water to dishes, to wash dishes automatically.
The dishwasher is provided with at least one rack in a tub for placing dishes thereon, a sump for holding washing water, and at least one spray unit for spraying washing water to the dishes.
In the related art dishwasher, the washing water is pumped from the sump to the spray unit, lead to a spray arm along a washing water pipe, and sprayed to the dishes.
The washing water washed the dishes is recovered to the sump, and supplied to the spray unit again for spraying to the dishes.
Such a repetitive use of the washing water leads to increase foreign matters in the washing water, gradually.
According to this, washing performance is impaired, and the foreign matter is liable to block a filter at the sump. If the filter is blocked, an excessive pressure become to exert to the filter, to result in deformation of the filter.